title: The conduction pore of a cardiac potassium channel.
abstract: Ion channels form transmembrane water-filled pores that allow ions to cross membranes in a rapid and selective fashion. The amino acid residues that line these pores have been sought to reveal the mechanisms of ion conduction and selectivity. The pore (P) loop is a stretch of residues that influences single-channel-current amplitude, selectivity among ions and open-channel blockade and is conserved in potassium-channel subunits previously recognized to contribute to pore formation. To date, potassium-channel pores have been shown to form by symmetrical alignment of four P loops around a central conduction pathway. Here we show that the selectivity-determining pore region of the voltage-gated potassium channel of human heart through which the I(Ks) current passes includes the transmembrane segment of the non-P-loop protein minK. Two adjacent residues in this segment of minK are exposed in the pore on either side of a short barrier that restricts the movement of sodium, cadmium and zinc ions across the membrane. Thus, potassium-selective pores are not restricted to P loops or a strict P-loop geometry.
authors.affiliation: Department of Pediatrics, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
authors.forename: K K
authors.initials: KK
authors.lastname: Tai
authors.forename: S A
authors.initials: SA
authors.lastname: Goldstein
mesh_terms: D000818:Animals; D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology; D004594:Electrophysiology; D006801:Humans; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D009154:Mutation; D009206:Myocardium / Q000378:metabolism*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D051381:Rats; D019789:Tetraethylammonium / Q000494:pharmacology; D014981:Xenopus
chemical_list: D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; C496911:Kcnq1 protein, rat; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; C059983:potassium channel protein I(sk); D002104:Cadmium; D019789:Tetraethylammonium